Description

Glaucoma is an optic neuropathy that is characterized by progressive structural and functional neuropathy. It is a leading cause of irreversible blindness.

Open angle glaucoma (OAG) is the commonest subtype of glaucoma. The number of patients diagnosed with POAG was estimated 52.68 million in 2020 and expected to be 79.76 million in 2040.

The management of OAG in patients with pseudophakia aims to IOP, which is the major modifiable risk factor for glaucoma progression. This can be achieved by medical, laser or surgical methods.

In many cases medical therapy can provide an effective IOP control, while surgery and laser are still indicated when the medical treatment fails to lower IOP sufficiently, or if the patient is not compliant with treatment.

Trabeculectomy with mitomycin C (MMC) is a filtration procedure that reduces IOP by creating a connection between the anterior chamber and the sub-conjunctival space after excision of a part of the trabecular meshwork. Pseudophakic eyes with OAG have a higher risk for surgical failure of trabeculectomy with MMC than the phakic eyes. Also it is associated with a higher incidence of complications as hypotony, lost anterior chamber or supra-choroidal effusion.

Laser therapy, as a cyclodestructive procedure, lowers IOP by reducing aqueous humor production. This is achieved through the application of diode laser energy to the sclera, which is absorbed by the melanin pigment in the ciliary processes, resulting in coagulative necrosis of the ciliary body. Historically, this treatment was regarded as a last-resort option for eyes with very limited visual potential due to the significant risks of uncontrolled inflammation and phthisis bulbi.

Now, with recent advances in laser probes and laser settings, the safety of trans-scleral cyclo-destruction has improved, rendering it a viable non-invasive option for a broader spectrum of patients including those with good visual acuity (VA) and as a primary procedure in management of OAG with pseudophakia.

Two approaches are commonly used to deliver laser energy using continuous wave trans-scleral cyclo-photocoagulation (CW-TSCPC): the conventional "pop" technique, where laser energy is initially increased until an audible, explosive, cavitating tissue-derived "pop" is heard. The laser power is then reduced until these pops are no longer audible. This method typically begins with a laser energy setting of approximately 1750-2000 mW, applied for a short duration of 2 seconds, and the treatment is delivered circumferentially along the limbus. In contrast, slow coagulation (SC) CW-TSCPC utilizes a lower amount of diode laser energy over an extended period, approximately 1250 mW over 4 seconds.

Previous results comparing the outcomes of the slow coagulation approach with the conventional high-energy pop approach found a lower incidence of postoperative complications in the slow coagulation group and comparable IOP- lowering effects between both groups. Although conventional CPC may have previously been reserved for blind painful eyes or eyes which have already failed prior glaucoma surgery, recent literature supports slow coagulation TSCPC (SC-TSCPC) as a reasonable primary option to lower IOP in eyes without prior incisional glaucoma surgery.

There have been few reports of SC-TSCPC being used as a primary surgical treatment in patients with glaucoma, and few studies published in the literature documenting the effect of SC-TSCPC in patients with good VA.